Method for acquiring and forming a spectrometry image and spectroscopic measuring device

Abstract

Disclosed is a method of acquiring and forming a spectrometry image of a sample including the following steps: e1) acquisition of an initial image, composed of pixels, of an area of the sample and definition of a maximum set of N, 2≤N, measurement positions of spectrometry, each measurement position including a coordinate and an intensity determined on the basis of the pixels; e2) assignment of a classification value to each of the N measurement positions on the basis of deviations, calculated based on an intensity difference and a coordinate difference, between the measurement positions; e3) determination of a group of P, 1≤P≤N, measurement positions as a function of the classification values; e4) successively, for each measurement position of the group, positioning of an excitation beam in the measurement position on the area of the sample, acquisition of a spectrometry measurement and formation of the spectrometry image.

The invention claimed is: 
     
       1. A method of acquiring and forming a spectrometry image (IS) of a sample ( 1 ) comprising the following steps:
 e1) acquisition of an initial image (II) of an area of the sample ( 1 ), the initial image (II) being composed of pixels, and definition of a maximum set of N, 2≤N, spectrometry measurement positions (PM), each measurement position (PM) comprising at least one coordinate (CX; CY), representative of the measurement position (PM) with respect to the area of the sample ( 1 ), and at least one intensity (IR 1 ; IR 2 ; IG 1 ; IG 2 ; IB 1 ; IB 2 ), determined on the basis of at least one pixel of the initial image (II) located in a neighborhood of the measurement position (PM); 
 e2) assignment of a classification value to each of the N measurement positions (PM) on the basis of deviations between the measurement positions (PM), a deviation between two measurement positions (PM) being calculated on the basis of an intensity difference (IR 1 ; IR 2 ; IG 1 ; IG 2 ; IB 1 ; IB 2 ) and a coordinate difference (CX; CY); 
 e3) determination of a group of P, 1≤P≤N, measurement positions (PM) among the set of N measurement positions (PM) as a function of the classification values assigned in step e2); 
 e4) successively, for each measurement position (PM) of the group determined in step e3), positioning of an excitation beam ( 2 ) at said measurement position (PM) on the area of the sample ( 1 ), acquiring a spectrometry measurement and constructing the spectrometry image (IS) based on the acquired spectrometry measurement(s). 
 
     
     
       2. The method according to  claim 1 , wherein the deviation between two measurement positions (PM) is calculated on the basis of a weighted sum of the square of the difference in intensity (IR 1 ; IR 2 ; IG 1 ; IG 2 ; IB 1 ; IB 2 ) between the two measurement positions (PM) and the square of the coordinate difference (CX; CY) between the two measurement positions (PM). 
     
     
       3. The method according to  claim 1 , wherein in step e2), the assigned classification values are all different from one another. 
     
     
       4. The method according to  claim 1 , wherein in step e3), the P measurement positions (PM) of the group are determined according to an ascending, respectively descending order of the classification values. 
     
     
       5. The method according to  claim 1 , wherein in step e2), a list S comprising the measurement positions (PM) whose classification value remains to be assigned and a list U comprising the measurement positions (PM) whose classification value is assigned are initialized, and the following steps e21) and e22) are iterated:
 e21) for each measurement position (PM) of the list S, determination of a total error by iterating steps e211), e212) and e213) of: 
 e211) moving of a considered measurement position from the list S to the list U; 
 e212) calculation of the total error associated with the considered measurement position on the basis of deviations between measurement positions (PM) of the list S and measurement positions (PM) of the list U; 
 e213) moving the considered measurement position from the list U to the list S; 
 e22) selecting a measurement position (PM) from the list S on the basis of each total error determined in step e21), assigning a classification value to the selected measurement position and moving the selected measurement position from list S to list U. 
 
     
     
       6. The method according to  claim 5 , wherein a classification value is initialized to a predetermined value and at each iteration of step e22), a classification value strictly lower, respectively higher, than the lowest, respectively highest, classification value is assigned to the measurement position (PM) with the lowest total error. 
     
     
       7. The method according to  claim 5 , wherein in step e212), the determination of the total error associated with the considered measurement position comprises the following steps:
 e2121) for each measurement position (PM) of list U, determination of the measurement position (PM) of list S with which the deviation is minimum, the value of the deviation between these two measurement positions (PM) defining a minimum deviation; 
 e2122) calculation of the total error on the basis of each minimum deviation determined in step e2121). 
 
     
     
       8. The method according to  claim 1 , wherein the group comprises at least three measurement positions (PM) and wherein a trajectory for carrying out the successive positionings of the excitation beam ( 2 ) is predetermined. 
     
     
       9. The method according to  claim 1 , wherein steps e3) and e4) are iterated and wherein at each new iteration, the group determined in step e3) comprises only measurement positions (PM) for which a spectrometric measurement remains to be acquired. 
     
     
       10. The method according to  claim 1 , comprising a step e11) of acquiring at least one spectrometry measurement in at least one predetermined measurement position, a predetermined classification value is assigned to each at least one predetermined measurement position. 
     
     
       11. The method according to  claim 1 , wherein the construction of the spectrometry image (IS) comprises the following steps:
 e41) for each measurement position (PM) for which a spectrometry measurement has been acquired, determining a spectrometry value based on said spectrometry measurement; 
 e42) for each remaining measurement position, determining a spectrometry value on the basis of at least one selected spectrometry measurement, which is selected as a function of the coordinate difference between said remaining measurement position and the measurement position (PM) at which said at least one selected spectrometry measurement was acquired. 
 
     
     
       12. The method according to  claim 11 , wherein in step e42), the selected spectrometry measurements are the spectrometry measurements acquired at measurement positions (PM) having a difference in coordinates with said remaining measurement position less than a threshold value. 
     
     
       13. The method according to  claim 10 , wherein, in step e42), the spectrometry value is determined on the basis of each selected spectrometry measurement weighted by the deviation between the measurement position (PM) at which the selected spectrometry measurement was acquired and said remaining measurement position. 
     
     
       14. The method according to  claim 1 , comprising a step e43) of interpolating the spectrometry image (IS) in which a plurality of interpolation coefficients is determined on the basis of the deviations between the measurement positions (PM). 
     
     
       15. The method according to  claim 1 , comprising a stopping measure to end, in step e4), the acquisition of additional spectrometry measurements. 
     
     
       16. The method according to  claim 1 , wherein the number of spectrometry measurements to be acquired is predetermined. 
     
     
       17. The method according to  claim 1 , wherein a region of interest, comprising only part of the measurement positions (PM), is predetermined in the initial image (II), and in step e3) the group is determined based on the measurement positions (PM) belonging to the region of interest. 
     
     
       18. The method according to  claim 1 , wherein at least one spectrometric measurement is spatially integrated over a sector of the sample ( 1 ). 
     
     
       19. The method according to  claim 1 , wherein the initial image (II) is acquired according to one of the following imaging methods:
 spectroscopic acquisition at one or more predetermined spectral bands; 
 optical acquisition in reflection or in transmission; 
 hyperspectral acquisition; 
 acquisition by atomic force microscope; 
 acquisition by scanning electron microscope. 
 
     
     
       20. A spectroscopic measuring apparatus comprising:
 a light source designed to generate an excitation beam ( 2 ); 
 a support adapted to receive a sample ( 1 ); 
 an image capture device; 
 a processor programmed to implement steps e1) to e4) of the method according to  claim 1 .